Elevated reservoir for use with off-shore oil wells

ABSTRACT

Elevated reservoir carried by platform which comprises a plurality of box-like sections, each of which is supported by a plurality of inclined pilings. Adjacent sections are spaced by ribs aligned with their sides and connected by prestressing cables extending through the ribs and box sides. The platform enables the piles to act as a unit in resisting horizontally applied forces.

United States Patent [151 3,648,466 Houdin et al. Mar. 14 1972 [54] ELEVATED RESERVOIR FOR USE 2,776,471 1/1957 Dobell ..52/228 X WITH OFF.SH()RE ()[L WELLS 3,173,226 3/1965 Solnick.... ....52/228 X 3,255,591 6/1966 Thornley ..6l/46 [72] Inventors: Henri lloudln, 18 rue Theodore de Banville, Paris; Rene Perm, 42 rue de Sevres, OTHER PUBLICATIONS Boulogne, both of France ClVll Engineenng (publication) of Jul. 1956 pp. 41, 42, 43. [22] Filed: May 4, 1970 [21] APPL 34,060 Primary Examiner-Jacob Shapiro AttorneyHolcombe, Wetherill & Brisebois [30] Foreign Application Priority Data [57] ABSTRACT May 5, 1969 France ..69l2401 Elevated reservoir carried by platform which comprises a rality of box-like sections, each of which is supported by a plu- [52] US. Cl ..6l/46, 61/50, 55226225605 ramy of inclined pilings. Adjacent sections are Spaced by ribs 51 1m. (:1. .3020 21/00 E02b 17/00 E04b 1/22 aligned with their Sides and by Ptesttesstttg cables [58 Field of Search ..6l/ 16 46.5, 50 32' 52/301 extending thmugh the ribs and sides- The Ptattotm 52/263, 5 bles the piles to act as a unit in resisting horizontally applied forces. [56] References Cited i m 4 W UNITED STATES PATENTS 3,466,878 9/1969 Esquillan et a1. l 1

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ELEVATED RESERVOIR FOR USE WITH OFF-SHORE OIL WELLS SUMMARY OF THE INVENTION This invention relates to an elevated reservoir having a large capacity.

As is well known, more and more off-shore oil wells are being drilled, and these require storage reservoirs of large capacity, for example 100,000 m. and up.

When the wells are drilled relatively close to the shore, the storage reservoirs may be built on the shore. When this is not the case, the storage reservoirs are commonly submerged near the wells.

These submerged reservoirs, however, require the presence of a sufficient depth of water near the well (generally at least 30 meters).

In practice, there are certain cases in which the well is so far from the shore that storage on the shore is not economical, but the depth of the water near the well is insufficient to permit the use of a submerged reservoir.

In order to meet this problem elevated reservoirs have been suggested, which are mounted on pilings so as to store the oil at a certain height above the level of the sea.

This solution solves the problem to the extent that it is possible to manufacture reservoirs of large capacity at a price low enough to make their adoption more economical than storage on the shore.

The present invention, which is the result of extensive research, relates to an elevated reservoir of large capacity, which has the necessary strength, and which may be built at a cost sufficiently low to render its use economically feasible.

It is the object of the present invention to provide, as a new article of manufacture, an elevated reservoir supported on pilings, which is characterized by the fact that it comprises a group of supports, each of which consists of at least one pile. These supports are regularly distributed beneath the body of the reservoir and connected to each other by a platform which distributes the horizontal forces applied to each of them among all the supports while being adaptable to slight vertical displacements of the supports which may result from sinking of the ground on which the piles rest. The body of the reservoir proper may be, for example, a cylindrical chamber made of metal plates resting directly on the platform.

In other words, the essential characteristic of the invention consists in building on the supports constituted by the piles a platform which has the ability to connect the supports so that they act as a unit to resist horizontally applied forces.

In one particular embodiment of the invention, each support consists of a group of piles inclined with respect to the vertical so as to resist horizontally applied forces and converging substantially to a point at the level of the platform.

In a preferred embodiment of the invention each support consists of two piles inclined to form an A, the tops of the piles being connected side by side (with respect to the plane of the A) substantially at the level of the platform.

in this preferred embodiment, the supports are uniformly distributed in a grid of squares. Moreover, the planes of the piles which constitute the different supports are alternately positioned parallel to each of the sides of the grid formed by the supports.

However, when the height of the piles is so great that the lower end of a pile from one support meets the lower end of a pile from another support, the plane of the piles is slightly inclined with respect to the directions of the network so as to prevent the two piles from interfering with each other.

The piles may be made in any way. However, it is particu larly advantageous to make the piles of prestressed concrete, according to the technique which consists of first boring a hole to receive the piles, using a metallic sleeve, and then introducing tubular concrete members, which are prestressed and constitute the pile after retraction of the metallic sleeve.

In one particular embodiment of the invention, the platform is made from boxes which are square in section, mounted on the tops of the piles constituting the supports and attached to the tops of these piles by means of concrete while being connected to each other by vertical concrete ribs in alignment with their sides.

It is advantageous to prefabricate these ribs which are then attached to the various boxes by means .of prestressing cables.

In this particular embodiment it is advantageous for the dimensions of the square boxes to be such that the width of the boxes corresponds substantially to the distance separating each two boxes. There is thus formed a grid of ribs defining square openings around the tops of the supports constituted by the piles. It is this grid of ribs which makes it possible to connect the supports so that they act as a unit to resist horizontal forces.

The platform itself may be made by pouring concrete directly into the boxes, in particular at the time the box is mounted on the top of the piles. On the other hand, the surfaces of the platform outside the boxes may advantageously consist of square prefabricated slabs which are mounted on the ribs.

It is a further object of the present invention to provide a method of making the platform which [has just been described, which method consists in producing the piles constituting a first support, mounting the first box on the upper ends of the piles constituting said first support and closing the top of this first box, manufacturing the piles constituting a second support adjacent the first, positioning in alignment with the two parallel sides of the first box, and in the direction of the second support, two prefabricated ribs which are attached to the first box by prestressing cables, mounting at the end of these ribs a second box, using prestressing cables, attaching the second box to the upper ends of the piles constituting the second support, positioning a prefabricated slab on the ribs between the two boxes, and thus proceeding step by step until the surface of the platform has been completed.

This process has the advantage of locating each of the boxes from a starting support without applying any force to the other supports, because the pilings constituting the other supports are attached to the various boxes only after the boxes have been placed in position.

It follows that the assembly of the platfonn is not affected by irregularities in the driving of the piles.

The tank proper may be of a conventional type. It consists, for example, of a casing of sheet steel with its bottom resting on the platform which has just been described, and having cylindrical vertical sides.

This type of tank imposes on the platform a load per m? which is uniformly distributed.

Elevated reservoirs may be made in this manner which have platforms capable of supporting loads up to 15,000 ing/m. and more. The construction of these platforms is sufficiently inexpensive to make the use of this type of reservoir economically practical. All safety requirements are also well satisfied.

In order that the invention may be better understood, one embodiment thereof will now be described purely by way of illustration and example, with reference to the accompanying drawings on which:

FIG. I is a vertical sectional view through one part of an elevated reservoir according to the invention;

FIG. 2 is a cross-sectional view taken along the line IIII showing one-fourth of the reservoir shown in FIG. 1, looking upward;

FIG. 3 is a cross-sectional view on a larger scale taken along the line III-III of FIG. 2; and

FIG. 4 is a cross-sectional view taken along the line IV-IV of FIG. 3 before the box at the right has been attached to its supports.

It will be seen that FIGS. 1 and 2 schematically illustrate a reservoir of large volume according to the invention. This reservoir is supported on pilings such as l, 1', 2, 2, the lower ends of which penetrate the submarine soil 3 passing through a sedimentary layer 4.

The upper ends of these pilings are high enough above the level of the sea to raise the platform above the direct effects of the waves. The depth to which the piles must be driven into the submarine soil is dependent on the weight to be supported and the characteristics of the soil and may be calculated by conventional methods.

In the embodiment described, the piles are made by assembling tubular elements connected end to end by prestressing cables. These tubular elements are introduced through a hole produced by a tube equipped with a drill.

FIG. 1 also shows the platform 6, which is fastened to the tops of the piles l, 1, 2, 2', and consists of slabs 7 and vertical ribs 8. The construction of the platform will be hereinafter described in a detailed manner.

The platform 6 supports the body 9 of the reservoir proper, which is cylindrical about a vertical axis and is made in a conventional manner from sheet steel.

In the embodiment described, the reservoir is 88 meters in diameter and 20 meters high, having a volume of about 120,000 mi.

The platform is about I2 meters above the surface of the water and the piles are about 60 meters long.

FIG. 2 is a schematic sectionalview taken just below the slabs 7 which shows the grid of ribs which form a square pattern.

This figure also shows schematically the tops of the piles l, l, 2, 2', as well as the directions of their lower parts, which are represented by arrows positioned axially of the piles.

As may be seen on FIG. 2, the directions of the piles of each group are alternated substantially in the two directions of the grid of ribs.

In effect, piles, 1, 1' run substantially east-west, whereas piles 2, 2' run substantially north-south, as shown in FIG. 2.

The group of piles, as seen from above, forms a plurality of lozenges since, allowing for the substantial length of the piles, the lower parts of the two piles of two adjacent supports would meet each other if the piles had been strictly parallel to the directions of the ribs.

As clearly shown in the drawings, the piles of a single support are not positioned in the same vertical plane but in two parallel planes so that the heads of the piles are positioned side by side and not opposite each other. This characteristic makes it possible to produce a better connection between the tops of the piles and to compensate more easily for differences in the length of the piles, which appear at their upper ends.

FIGS. 3 and 4 show the structure of the platform 6 on which the reservoir rests.

The platfonn is made from prefabricated boxes 10 which, as may be seen on FIGS. 2 and 3, consist of four equal sides 11 which are attached to each other and connected by a bottom 12 which is provided with an elongated opening 13 large enough to receive the upper parts of the pile l, l, or 2, 2', forming a single support.

As may be seen in FIG. 4, the sides 11 project slightly toward the outside at 11' to meet the ribs 8 which are positioned in alignment with the sides 11 and serve to connect two adjacent boxes.

In order to construct the platform, the pilings of a first support are first placed in position.

A first box (for example box A in FIGS. 3 and 4) is then positioned and held in place while the concrete 14 is poured to connect the two upper ends of the piles l and l and seat the box A on these piles.

As will be seen at A on FIG. 4, the concrete 14 is H shaped in plan and the middle bar of the II is positioned substantially along the line connecting the median points of the upper ends of the piles.

Of course, the opening 13 in casing A (which is not shown for greater clarity on FIG. 4) is longest in the direction of the transverse bar of the H of the concrete. The slab 15 (FIG. 3) is then put in position and closes the upper part of the casing while constituting part of the platform.

The two piles 2, 2' are then put in position to constitute a second support.

Two prefabricated ribs 8 (FIG. 4) are then mounted in a conventional manner in alignment with the two parallel sides 11 of the box A, using prestressing cables 16 which pass through both the sides 11 and the ribs 8.

A box B is then positioned in alignment with the ribs 8, (for example using aderrick resting on the slab l5). Prestressing cables 16 are used for this purpose. This results in an accurate positioning of the box B with respect to the box A since the various components of the boxes and the ribs 8 are placed under stress.

The pilings 2 and 2' are then connected to each other and to box B with concrete, proceeding as indicated in the case of box A. (FIG. 4 shows the platform before the concrete has been added to box B, whereas FIG. 3 shows it after concrete has been added to box B).

It then suffices to position a prefabricated slab 7 on the ribs 8 which connect the boxes A and B so as to produce a continuous surface running from box A to box B.

In order to produce the platform it suffices to proceed step by step in the manner described, in the two directions of the grid of supports.

It will be seen that by operating in this manner a platform is produced in which all the ribs are under longitudinal stress before the boxes are attached to the pilings, which makes it possible to produce a platform having great horizontal rigidity without placing any strain on the piles.

It is thus possible to construct in a simple and economical manner a platform according to the invention which enables all the supports to act as a unit in resisting horizontally applied forces but which tolerates slight vertical uneveness in the supports. By way of example, calculations show that a platform such as the one which has just been described and in which the supports are about 10 meters apart will tolerate relative vertical displacements up to 2 cm. between one support and the next.

It will of course be appreciated that this embodiment has been described purely by way of illustration and example, and may be modified as to detail without thereby departing from the basic principles of the invention as defined by the following claims.

What is claimed is:

1. Method of manufacturing a support for a reservoir which comprises the steps of emplacing a plurality of piles to form a first support, positioning a first box on this support, fastening this box to the ends of the piles constituting said first support, covering the top of this first box, emplacing a plurality of piles to form a second support adjacent the first, positioning two prefabricated ribs in alignment with two sides of the first box which extend in the direction of the second support and attaching them to the first box by means of prestressing cables, attaching a second box to the end of these ribs by means of prestressing cables, fastening the second box to the upper ends of the piles constituting the second support, mounting a prefabricated platform component on the ribs between the two boxes and thus proceeding step by step to complete the structure.

2. Method as claimed in claim 1 comprising the steps of attaching said boxes to said piles with concrete.

3. Pile-supported elevated reservoir comprising:

a tank,

a platform supporting said tank and comprising a plurality of horizontally spaced prefabricated boxes,

at least one pile supporting each box and having its upper end received therein,

prefabricated ribs in alignment with the sides of said boxes and connecting adjacent boxes, and

prestressing means extending longitudinally through the sides of said boxes and the ribs aligned therewith.

4. Reservoir as claimed in claim 3 in which each of said boxes receives the ends of at least two piles, the piles of each box being inclined with respect to the vertical, and converging at the level of said box.

5. Reservoir as claimed in claim 3 in which the sides of said boxes and said ribs define two sets of parallel lines which intersect each other at right angles.

equal to the length of a rib.

9. Reservoir as claimed in claim 3 in which the said tank is made of sheet steel, is cylindrical in form. and has a vertical axis.

10. A reservoir as claimed in claim 3 in which each of said boxes contains concrete surrounding the upper end of a pile therein.

i t t 

1. Method of manufacturing a support for a reservoir which comprises the steps of emplacing a plurality of piles to form a first support, positioning a first box on this support, fastening this box to the ends of the piles constituting said first support, covering the top of this first box, emplacing a plurality of piles to form a second support adjacent the first, positioning two prefabricated ribs in alignment with two sides of the first box which extend in the direction of the second support and attaching them to the first box by Means of prestressing cables, attaching a second box to the end of these ribs by means of prestressing cables, fastening the second box to the upper ends of the piles constituting the second support, mounting a prefabricated platform component on the ribs between the two boxes and thus proceeding step by step to complete the structure.
 2. Method as claimed in claim 1 comprising the steps of attaching said boxes to said piles with concrete.
 3. Pile-supported elevated reservoir comprising: a tank, a platform supporting said tank and comprising a plurality of horizontally spaced prefabricated boxes, at least one pile supporting each box and having its upper end received therein, prefabricated ribs in alignment with the sides of said boxes and connecting adjacent boxes, and prestressing means extending longitudinally through the sides of said boxes and the ribs aligned therewith.
 4. Reservoir as claimed in claim 3 in which each of said boxes receives the ends of at least two piles, the piles of each box being inclined with respect to the vertical, and converging at the level of said box.
 5. Reservoir as claimed in claim 3 in which the sides of said boxes and said ribs define two sets of parallel lines which intersect each other at right angles.
 6. Reservoir as claimed in claim 4 in which a line drawn through the centers of the piles in each box at the level of the platform is at right angles to a line drawn through the centers of the piles of each adjacent box at the same level.
 7. Reservoir as claimed in claim 3 in which said ribs and boxes support slabs constituting the upper surface of the platform.
 8. Reservoir as claimed in claim 5 in which the boxes are square with the length of one side of each box substantially equal to the length of a rib.
 9. Reservoir as claimed in claim 3 in which the said tank is made of sheet steel, is cylindrical in form, and has a vertical axis.
 10. A reservoir as claimed in claim 3 in which each of said boxes contains concrete surrounding the upper end of a pile therein. 